When a color image is copied, printed or faxed on a black-and-white rendering device, the colors are converted to shades of gray. Two different colors with the same luminance or perceived brightness may “map” to the same shade of gray, making it impossible to interpret the information that the colors carry. When such a situation occurs on graphics such as pie charts or bar charts, two colors will appear the same and the chart loses its information value.
When converting color images to black and white bitmaps for printing or storing, the color information is usually lost and cannot be recovered. Some methods address this issue, and encode the color information into the black and white image by using some form of visible textures. The visible textures, however, may sometimes appear uneven and difficult to discern. Such textures also strongly imply that the areas with different textures should be treated differently, even when one does not intend to differentiate between them.
While trying to determine how to retain the information conveyed in color images, researchers have searched for new techniques to represent color images in black and white. Some methods transform each color into a microscopically different texture or pattern in the gray portions of an image. By implementing such a method, it is relatively easy to identify colors with similar luminance value, thereby making the pictures more pleasing and useful. Thus, by mapping the color to textures in this manner, the textures can be later decoded and converted back to color.